The nucleotide sequence of the tRNA primer binding site of Prague B strain of avian sarcoma virus genome RNA will be determined. Sequence analysis will be performed on DNA isolated from the cytoplasm of chicken cells three days after infection. This DNA will be ligated in lambda ch21A DNA and clones will be screened for those which contain the region of interest. The gene organization and structure of selected mouse cell tRNA genes will also be studied after cloning these genes in bacteriophage lambda. Gene copy number and possibly tRNA gene clustering will be analyzed by hybridization to restriction enzyme digests of cell DNA. Organization and sequence will be analyzed using representative tRNA gene clones. Emphasis will be placed on those tRNA genes whose products are associated with the genome RNA of RNA tumor viruses.